1. Field of the Invention
This invention relates to an image sensor package, and more particularly to an image sensor package structure free of particle contamination on micro lens, and the method for manufacturing the same.
2. Description of the Prior Art
The semiconductor technologies are developing very fast, and especially semiconductor dice have a tendency toward miniaturization. However, the requirements for the functions of the semiconductor dice have an opposite tendency to variety. Namely, the semiconductor dice must have more I/O pads into a smaller area, so the density of the pins is raised quickly. It causes the packaging for the semiconductor dice to become more difficult and decrease the yield. The main purpose of the package structure is to protect the dice from outside damages. Furthermore, the heat generated by the dice must be diffused efficiently through the package structure to ensure the operation the dice. Most of the package technologies divide dice on a wafer into respective dice and then to package and test the die respectively. Another package technology, called “Wafer Level Package (WLP)”, can package the dice on a wafer before dividing the dice into respective dice. The WLP technology has some advantages, such as a shorter producing cycle time, lower cost, and no need to under-fill or molding.
A digital image technique has been wildly applied to image shooting instrument such as digital camera, image scanner, etc. The conventional CMOS sensor is disposed on a circuit board. The CMOS sensor has a chip secured therein. The lens seat has a focusing lens for focusing the image onto the chip of the CMOS sensor. Through the lens, the image signal is sent by the chip to a digital processor for converting the analog signal into digital signal. The Chip of the CMOS sensor is relatively sensitive to infrared ray and dust particles. If the unwanted particles are not removed from the sensor, it leads to downgrade the quality of the device. In order to achieve the purpose, the removal by manual may damage the sensitive chip. Typically, the image sensor module is formed by using a method of COB or LCC. One drawback of the COB is lower yield rate during packaging process due to particle contamination on sensing area. Besides, the drawbacks of the LCC are higher packaging cost and lower yield rate due to particle contamination on sensing area.
Further, micro lenses are optical components on semiconductors utilized as solid state imaging devices. One of the most important considerations in designing and manufacturing micro lenses is photosensitivity. One reason micro lens photosensitivity may be reduced is that the area of each micro lens has been reduced below an optimum value. Moreover, SHELL CASE company also develops wafer level package technique, the image sensor dice packaged by the SHELL CASE is higher cost due to requiring two glass plate and complicate process. And, the transparency is bad due to epoxy wearing out, and the potential reliability may be reduced. U.S. Pat. No. 5,514,888 for ON-CHIP SCREEN TYPE SOLID STATE IMAGE SENSOR AND MANUFACTURING METHOD THEREOF; issued May 7, 1996 to Yoshikazu Sano, et al. teaches a method for forming charge-coupled devices (CCDS) on a silicon substrate. A micro lens array is formed over the CCD array using conventional lithography and re-flow techniques.
Wire bonding technology is a conventional technique used to make electrical connections within the package. Wire bonding may employ gold, aluminum, or copper wires. A wire is bonded at one end to the chip and at the other end to a next-level substrate such as a lead frame, a printed circuit board, a ceramic substrate, or a flexible circuit board.
A conventional technique of wire bonding is to form a ball bond on the chip and a stitch bond on the substrate. More particularly, a ball is formed on a tail of the wire, which extends from the end of a capillary of a wire bonder, and is bonded to a bond pad of the chip under pressure by the capillary while heat and/or ultrasonic vibration are applied. After the ball bond is formed, a loop is formed in the wire by subsequent action of the capillary. The capillary deforms the wire against a bond position of the substrate, producing a wedge-shaped stitch bond.
Therefore, what is desired is to provide a novel image sensor package structure free of particle contamination on sensing area and improving traditional wire bonding connect.